680 



Marine Aiicrobiolooy 



K 

 time in days 



26 



Fig. 4. Decrease of sulfate and increase of sulfide in a medium inoculated 

 with a suspension of anaerobic mud. 



amounts in the first experiment to 0.174 mg/g wet sediment and 

 in the second to 0.372 mg/g wet sediment after eight and four 

 days. The sulfur must have derived from another source than 

 from the sulfate: e.g. the originally organic bound sulfur. The in- 

 crease of the sulfides of the first experiment was 0.387 mg/g wet 

 sediment after eight days and 0.870 mg/g wet sediment in the 

 second experiment after four days. The share of the originally 

 non-sulfate bound sulfur amounts in experiment (1) to 45.36 

 per cent and in the experiment (2) to 42.77 per cent. As expected, 

 all bacterial numbers were higher than in the first series of ex- 

 periments. Again the aerobic bacteria showed the highest num- 

 bers, followed by the anaerobes, the organic-HoS-producers and 

 the sulfate-reducers. The sulfate-reducers were about 1000 times 

 less than the organic H.S-producers, but the absolute number was 

 even more than in the first setup. The increase or decrease of the 

 bacterial numbers are shown in the figure. 



Figure 5b shows experiments which were conducted in Hel- 



